Present-day motor vehicles are designed so that, regardless of the operating mode of the vehicle, which may be the parking mode with the engine switched off or the movement mode with the engine running, it is possible to check the open or closed state of a plurality of contacts such as a door closure contact, a trunk closure contact, a headlight activation lever contact, a windshield wiper activation lever contact, and the like.
To this end, motor vehicles are fitted with an electronic unit or computer comprising:                a microcontroller having a plurality of communication ports and programmed to control the periodic acquisition of signals representative of the state of contacts, by alternating time intervals of acquisition of said signals with standby time intervals,        an electrical circuit for supplying power to each of the contacts and for connecting each of said contacts to a communication port.        
The disadvantage of this acquisition method lies in the potential harmful consequences that may be caused by the occurrence of an electrical fault of the short-circuit type.
This is because an electrical fault at one of the contacts causes an electric current to be injected into each of the communication ports of the microcontroller. In the acquisition time intervals, this current generated by the electrical fault is usually found to be less than the current consumed by the microcontroller, so that the microcontroller is not affected by the electrical faults.
On the other hand, notably in the case of the latest generation of vehicles in which the computer's power consumption in parking mode is very low, notably in order to prevent battery discharge, the current generated by an electrical fault may exceed the amount of current consumed by the computer, resulting in damage to the electronic components of the computer.
At the present time, the only solution proposed for overcoming this drawback is that of providing the computer with components capable of blocking the current generated by electrical faults that may occur. However, this solution tends to complicate the design of the computer and entails additional manufacturing costs.